How do you utilize a person in your organization that isn't fitting where they are assigned?

If they Can and have done the job, meeting thier obligations, yet we see a better position that needs to be filled and this Sm has the talent to do it.. USE THEM, reward as apropret.

If they are unwilling or unable to fulfill thier obligations in assigned duties then note that on evaluations, mentor and train till opportunities are exhausted, then move them to a position they can do no harm while you work seperation.
The caveat to that wold be if they were thrust into a position they are not equipped for, not trained for, not certified for by MOS or career field..if they tried but were unable to fulfill duties in this additional duty or odd assignment them no harm no foul.. Move them to an authorized assignment within their assigned specialty and move on.
If the unit needs a gynecologist, the commander may be in the legal athority to assign me to that position, but as Im neither trained, nor qualified to hold the position, my failure to look at that anatomy in the correct light and manner is not to be held against me... I may be personally familiar with the body feature in limited use and scope.., but that does not = the knowledge or experience to know what to do medically in the assignment of gynecologist..thus my failure should not be held against me.

As an example, if they can't do the MOS regardless of how much training and re-training has been conducted, and if their other skills include Admin and they are good at it, then they would become my office weenie doing DTMS, DTS, MEDPROS, etc. Otherwise, I would sit them down and find out if they want to reclass to something else and help facilitate that. Just because they aren't good at one job doesn't mean they are bad at others.

1st question - Does the person have the desire to be part of the team? Their frustration at the mismatch may mask that desire.
2nd question - If they have the desire, what is the best match between their skills/strengths and the team's needs? Doesn't matter for what they were earmarked.